1. Field of the Invention
This invention relates to an abnormality detecting system for a DC motor control apparatus which drives a DC motor at a revolving speed following a command speed signal.
2. Description of the Prior Art
In a DC motor control apparatus of the type in which a tachogenerator or a like speed detector is coupled with a DC motor to perform drive control of the DC motor in accordance with a signal corresponding to the difference between a DC motor revolving speed signal from the speed detector and a command speed signal to drive the DC motor at a revolving speed represented by the command speed signal, if no revolving speed signal is provided due to a trouble of the speed detector, the abovesaid difference signal is not obtained, so that the revolving speed of the DC motor rises abnormally high to put the DC motor in a runaway state, possibly developing trouble in a load driven by the DC motor.